1. Field of the Invention
The invention relates to a plain bearing for necks of the rolls of rolling mills comprising a bearing bushing of metal and a plain bearing alloy introduced into it and based on tin with antimony and copper.
2. Description of the Related Art
Such bearings have been produced for many years, for example, as oil film bearings. The employed plain bearing alloy, however, is relatively soft so that it flows easily when under load. This flowing results in a loss of shape stability and requires a relatively quick exchange of the bearings for new or reworked bearings. Moreover, the resistance to pressure of the plain bearing alloy is relatively small.
It is also known to add cadmium to the known plain bearing alloys by which measure it was possible to increase the resistance to pressure. Cadmium-containing alloys, however, are no longer used as a result of their toxicity despite their advantages with respect to the resistance to pressure. Therefore, the known plain bearing alloys have been used again.
From EP 0 717 121 B1 plain bearing alloys are known which, by addition of silver and zinc, have the advantage of a higher compression limit and an improved repeated impact flexural load. These new alloys are used primarily in turbines, compressors, pistons and expansion engines. The advantage is that no toxic components are added to the plain bearing metal. The use of these alloys for necks of rolls, however, has not been easily possible in the past because the alloy components according to this prior art fluctuated widely so that the required minimal flow properties and the great resistance to pressure could not be realized in the desired way.
It is an object of the invention to improve a known plain bearing as well as a method for producing the plain bearing such that an excellent shape stability is provided as a result of minimal flow tendency and a high resistance to pressure so that, as a result, the bearings experience a long service life.
For this purpose, the plain bearing alloy is composed of 6.8 to 7.2 percent by weight antimony, 6.3 to 6.7 percent by weight copper, 0.5 to 0.7 percent by weight zinc, 0.05 to 0.15 percent by weight silver, an tin as the remainder. It was found that the use of such a plain bearing alloy significantly increases the shape stability and the resistance to pressure.